Channel-type induction furnaces are used for preparing, preheating, mixing and storing molten metals which are subsequently delivered to recipients, such as ladles or foundry moulds. In channel-type induction furnaces a bath of molten metal is connected with at least two channels intersecting one another. Heating of the metal is effected by an electrical field associated with the channels.
Such induction furnaces are disadvantageous in that movement of metal in the channels, and hence heating of metal in the bath, is effected only by convection and electrodynamic forces during interaction of electrical current within the mass of molten metal with the magnetic field. The movement of metal is a result of a thermal action of the current flowing through the furnace channel.
One proposal to overcome this problem is contained in U.S. Pat. No. 3,502,781, wherein there is provided an additional magnetic conductor having windings for inducing a controlled magnetic field interacting with the current flowing through the point of intersection of the channels, so as to cause the molten metal to flow in a given direction at a controllable speed.
This prior art structure requires the use of three different magnetic cores, each fed by direct current voltage and is confined to heating in three channels. The energy density which can be brought to bear on the molten metal is limited in this structure, so that the size of the furnace is correspondingly limited.
The electrical fields which are applied in the prior art structure cause motion of the molten metal within the channels, typically downwardly in peripherally-located channels and upwardly in the centrally-located channel, and flow within the molten metal bath by vertical and radial motion within the bath. This procedure causes turbulence at the surface of the bath and hence continuous exposure of the bath to oxidation.